The construction industry commonly uses single ply membranes to provide a waterproof barrier on flat or low-slope roofs. It is prohibitively expensive and difficult to produce and transport a single membrane that is sized to cover an entire roof surface, thus, a plurality of individual membranes are provided and oriented in an overlapping arrangement. The overlapping portions, or splices, of these individual membranes must be secured together to ensure that the plurality of membranes form a single waterproof surface. In addition, the outer edges of the membranes adjacent to the roof edge, as well as edges of the membrane surrounding objects on the roof surface, must be sealed in some manner to ensure that water does not intrude beneath the membranes.
In many cases, flashing is used to seal the edges of the roofing membranes. The flashing is similar to the single ply membranes used to cover the roof surface, but is provided in narrow strips and does not include reinforcements, such as a mesh fabric, which is provided in the membranes. Flashing, like the roofing membranes, may be provided as a thermoplastic material or a thermoset material. Thermoplastic flashings are capable of being heat welded to other thermoplastic materials, whereas thermoset materials require an adhesive bonding.
Both thermoplastic and thermoset flashings are available with or without a pre-applied adhesive. Thermoplastic flashings provided without an adhesive may be heat welded to other thermoplastic materials or may be adhered to other surfaces with adhesive bonding agents. Thermoset flashing provided without adhesive is adhered to other surfaces, including roofing membranes, by adhesives provided on site.
A common occurrence in roofing systems is the need to adhere flashing on one side to a thermoplastic membrane, and on another side to a metal or other non-heat weldable surface. The non-heat weldable surface may include an edge metal flashing (Gravel Stop), available under the trade names Firestone UNA-Edge, Firestone Drip Edge or Firestone Gravel Stop (Firestone). The non-heat weldable surfaces may also include a welded curb flange, flue flanges, or any other metal flanged penetrations. In addition, the non-heat weldable surface may be a thermoset membrane. Where a thermoplastic flashing is provided with a pre-applied adhesive on one surface, the adhesive binds the flashing both to the thermoplastic membrane as well as the non-heat weldable metal surface. Where a thermoset flashing is provided without a pre-applied adhesive, the flashing must be secured to both the thermoplastic membrane and the metal surface by an adhesive applied on site.
The ability to heat weld the thermoplastic flashing to the thermoplastic roofing membrane is advantageous in that it provides an excellent seal against water infiltration. Thus, a thermoplastic flashing without a pre-applied adhesive is attractive in that respect. However, the need to apply an adhesive on site between the thermoplastic flashing and the metal surface increases the labor, time, and cost involved in installation. Furthermore, conventional thermoplastic flashing assemblies require a termination bar or counter flashing at the edge of the thermoplastic flashing to provide a watertight seal, which is not provided by the bonding adhesive.
Thus, there exists a need in the art for a thermoplastic flashing laminate that is capable of providing a strong seal between a thermoplastic roofing membrane and a metal surface, while reducing the labor and costs involved in installation.